<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            /* 设置高度，宽度自适应 */
            height: 300px;
            /* 让父级弹性布局 */
            display: flex;
            flex-direction: column;
            /* 主轴方向 对齐方式*/
            /* justify-content: space-between; */
            background-color: pink;
        }

        .box1{
            width: 300px;
            height: 100px;
            background-color:skyblue;
        }
    </style>
</head>

<body>

    <div class="box">
        <div class="box1">
        </div>
        <div class="box1"></div>
        <div class="box1"></div>
    </div>
</body>

</html>